Method and apparatus for vacuum sealing packages and the like



Sept. 27, 1960 Filed March 51, 1959 PACKAGES AND THE LIKE 6 Sheets-Sheet 1 v (D \J II a INVENTOR.

JAMES Am /mm BY orro R. WEBER ATTORN YS Sept- 27, 1960 J. R. CHAPMAN ETAL 2,953,877

METHOD AND APPARATUS FOR VACUUM SEALING PACKAGES AND THE LIKE Filed March 31, 1959 6 Sheets-Sheet 2 \5 NIOZ 7 H4 04 O sq I03 v r 1 104 -15 [OI FIG. l3 l5:

INVENTOR. W JAMES R. CHAPMAN T .65 BY OTORWBR Sept. 27, 1960 J. R. CHAPMAN EI'AL 2,953,877

METHOD AND APPARATUS FOR VACUUM SEALING PACKAGES AND THE LIKE Filed March 31, 1959 6 Sheets-Sheet 3 INVENTOR. JAMES R. CHAPMAN OTTO R- WEBER BY ,w WV

ATTORNF Sept. 27, 1960 J. #2. CHAPMAN ETAL 2,953,877 METHOD AND APPARA s R VACUUM SEALING PACKAGE N HE LIKE Filed March, 31, 1959 6 Sheets-Sheet 4 I INVENTOR. JAMES R. CHAPMAN BY OTTO R. WEBER AT ORNEYS Sept. 27, 1960 J. R. CHAPMAN ETAL METHOD AND APPARATUS FOR VACUUM SEALING PACKAGES AND THE LIKE 6 Sheets-Sheet 5 Filed March 31, 1959 mQ v:

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INVENTORS' JANES R. CHAPMAN OTTO R. WEBEP ATTORNEYS OON Sept. 27, 1960 J. R. CHAPMAN ETAL 2,953,877

METHOD AND APPARATUS FOR VACUUM SEALING PACKAGES AND THE LIKE- Filed March 51, 1959 6 Sheets-Sheet 6 I05 AL INVENTORS' JAMES R. CHAPMAN OTTO R. WEBER ATTORNEYS METHOD AND APPARATUS FOR VACUUM SEALING PACKAGES AND THE LIKE Filed Mar. 31, 1959, Ser. No. 803,321

24 Claims. ((11. 53-42 This application is a continuation-impart of our pending application Serial Number 702,415, now. abandoned. V

This invention provides an improved method. and apparatus for vacuum sealing a package without the necessity of enclosing the main 'body thereof in a vacuum chamber, and without the use of hollow needles or nar' row suction tubes, and while such body is exposed to atmospheric pressure. 7

Packages, such as pliable foil bags made of aluminum, or the like, and containing solid or comminuted filling material, have been vacuum sealed at the filling throat, or other aperture, while the main body of the package has been exposed to the atmosphere. However, a hollow needle or small suction tube has been placed in or ad'- jacen-t the throat to produce a vacuum directly in the throat and package. When a vacuum begins to be es tablished, the throat collapses inwardly under the atmospheric pressure surrounding the throat, and thus prevents the proper outward airflow to produce the desired vacuum. It has been suggested that a sub-atmospheric chamber be provided around the throat, and that such chamber be maintained at a lower pressure vacuum than is produced inside the bag, such chamber being reduced to low pressure by means of separate passages or systems. Such constructions are relatively complicated and expensive, and the hollow needles or small suction tubes tend to become clogged by the accidental flow of filling material or refuse into such needles or small tubes. Y

An object of this invention is to overcome these prior disadvantages by a simple and inexpensive method and apparatus which does not utilize such hollow needles or small tubes within the throat of the bag and which automatically establish a lower pressure around the throat of the bag than is being produced within the throat and bag without the use of additional passageways and chamber, and in which such conditions are maintained until the desired low pressure vacuum is obtained within the bag.

This is accomplished by closing the outer end of the throat, puncturing or otherwise providing small or restrictive apertures in the side walls of the throat, loosely surrounding the outer surfaces of the throat with opposed rims or faces of a divided vacuum chamber which can be placed in communication with a vacuumpump or the like by relatively large pipes. These large pipes do not clog, and are capable of producing a low pressure zone within the chamber and around the outer surfaces of the throat while the inside of the throat is being reduced in pressure slowly by the slow outward fiow of air from the bag through the restrictive apertures and into the surrounding vacuum chamber. The higher pressure thus automatically rnaintained inside the throat prevents the throat from collapsing inwardlyuntil the desired vacuum is obtained within the bag. Thereafter, the throat is sealed by the said rims or faces, which are further pressed to gether to seal the throat between the restrictive apertures and the main body of the bag.

Another object of this invention is to provide mechanism A 2,953,877, Patented Sept. 27, 1 960 2 to produce a cycle of operations as described the foregoing object, together with initiating means to initiate the cycle of operations and program means automatically to maintain the mechanism in operation throughoutsuch cycle and then to stop the mechanism in readiness to per: form another cycle.

Another object of this invention is to utilize the velocity fall in head pressure (change to kinetic energy) of the air flowing at high velocity around the outside ofLthe' throat and inside the rims or faces of the ch mber to aid in maintaining a lower pressure outside the throat, while the inside of the throat is being slowly evacuated; I

Another object of this invention is to provide a piercing pin which has a thin supporting body an'd an enlarged piercing head to pierce a restricted aperture in the wall of the package through which a restricted flow 'o'fair may pass while the thin supporting body of the pin remains'in the aperture. 1 I Further objects of this invention will become apparent as the description proceeds with reference to the growth panying drawings in which: i

Figurel is a front view, in perspective, of an a paratus embodying this invention. g V V Figure 2 is a rear view, in perspective, of the apparatus shown in Figure l, and showing connections to auxiliary apparatus. I M V Figure 3 is an exploded view of the apparatus show'ri in Figure 1. I p p Figure 4 shows another embodiment of one of the bars shown in Figures 1, 2 and 3. p L

Figure 5 is an enlarged cross-section taken along the line 5-5 of Figure 1, turned and showing" a portion of the throat of the package inserted between the sealing bars. I

Figures 6, 7 and 8 show later positions of the b'ars shown in Figure 5. f-Figure 9 is a view, similar to Figure 5, with the bar shown in Figure 4 substituted for the lower bar of FigureS.

Figure 10 is an enlarged transverse crossfisecti'on of the lower bar shown in Figure 7. 1

Figures 11 and 12 show other embodiments of the ends of piercing pin.

Figure 13 is a wiring diagrainfor the apparatus disclosed herein. 7 V

Figure 14 is a view of another embodiment of this iiiventi'on, the view being partly in vertical cross-section along the line 14 -14 of Figure 15, and partly diagrammatic.

Figure 15 is a top plan view of a portion of Figure '14, on a reduced scale. V

Figure 16 is a view taken along the line 16'=-16o'f Fi ure 15. i 1

Figure 17 is a cross-section of a portion of an apparatus similar to that disclosed in Figures 1446 and showing 7 7 4 between them. The threat end 9 is closed by ridges 1t) and 11 (Fig. 6) extending from the faces 8 antl'7 and having resilient mounting means of springs '12 to cause the ridges 10 and 11 to meet and close the end 9'bf"the throat before the full relative travel of the bars 5 and'fi toward each otherhas taken place; Vacuum chamber opposed cavities 13 and 14 are'fojrmed in theifacesi i be described, to produce the relative movement between the supporting members or bars 5 and 6, to pierce the apertures 17 in the throat 3 (Fig. 6) to produce a zone of relatively low vacuum in the vacuum chamber formed by the cavities 13 and 14 and between the faces 7 and 8 and the outer surfaces of the sides 1 and 2 of the throat (Fig. 7), to reduce the pressure in the throat and package by outward fiow of air through the apertures 17 and past the thin body of the pin 16 into the vacuum chamber, and'then to seal the sides of the throat to each other (Fig. 8) by further movement of the bars 5 and 6 toward each other. This automatically separates the sides 1 and 2 of the throat 3 (Fig. 7) to permit a proper vacuum to be produced in the bag 4 without the use of complicated additional vacuum chambers or hollow needles.

The apparatus so far described may be assembled with and supported by other elements shown in Figures 1, 2, 3, 14 and 15. For example, the apparatus shown in Figures 1, 2 and 3 may include the end frame pieces 20 having feet 21 for attaching the apparatus on top or on the side of a supporting block, not shown, by means of clamps, bolts, or screws (not shown) passing through the feet 21. The end pieces 20 are bridged and secured together by means of the top plate 24 which is attached to the members 20 by means of screws 26 which pass through holes 28 in plate 24 and into the tapped holes 27 in the end members 20.

The end support members 20 have bearing receiving slots 30 and stationary bar receiving. slots 31. A continuous notch 33 is formed on the inner faces of the members 20 between slots 30 and 31 slidably to receive the movable bar 5, while the stationary bar 6 is received in the slot 31.

The stationary bar 6 is provided with tapped openings 38 which are aligned with openings 39 in the feet 21 and in end members 20 for the reception of screws 40 to secure the stationary bar 6 in place.

place.

The movable bar 5 rides in the slots 33 on the inner faces of the end members 20. Compression springs 42 are placed in openings 43 in the stationary bar 6 and similar openings, not shown, in movable bar 5. These springs resiliently urge the bars apart.

End bearing plates 44 have cylindrical bearings 45 to receive the shaft ends 46 and 46a of the eccentric 47. The bearings 45 are inserted in the slots 30, and the plates 44 have slots 50 for adjustable attachment to the end members 20 by means of the screws 52 which pass through the slots 50 into the tapped openings 53 in'the end support members 20. One shaft end 46a of the eccentric 47 has a handle 18 attached thereto and rotationally fixed thereon by means of the screw 55.

The eccentric 47 is adjustably mounted on the end members 20 as heretofore described, and bears downwardly on the top of movable bar 5 to move the bar 5 the desired distances to and from the stationary bar 6.

Referring now particularly to Figures 5, 6, 7 and 8, as well as to Figures 1, 2, 3, l4 and 15, the apparatus is adapted to receive a package, such as a bag, having a main body 4 in which the contents 61 to be preserved are placed. The bag has an evacuating throat 3 with sides 1 and 2 which is adapted to be placed between the bars 5 and 6. Initially the bag throat 3 is open at the end 9 as shown in Figure 5. The throat is then closed at the end 9 and pierced at apertures 17, as shown in Figure 6. Air is withdrawn from the body 4 to the de,-

4 sired degree of vacuum through apertures 17, as shown in Figure 7. The throat 3 is sealed by further movement of the bar 5 toward the bar 6 as shown in Figure 8, in a manner to be more fully described.

The throat 3 originally may be of any shape, such as substantially cylindrical in form, and eventually is pressed into a double-sided throat having sides 1 and 2, or the throat previously may have been pressed into the double sided form. The throat is inserted between the bars 5 and 6 to a point where the main body of the bag 4 and the contents 61 are near the front edges 68 and 69 of the bars 5 and 6 respectively. The positions of the throat and bag are shown in dotted lines in Figure 4 and in full lines in Figures 5-8. The bars 5 and 6 have opposed substantially flat and parallel faces 7 and 8 respectively, adapted to receive bag throats of various sizes. Opposed throat and closing ridge members 10 and 11 extend in front of the opposed faces 7 and 8. These ridge members are resiliently mounted by placing them in grooves 77 and 78 in which two or more springs 12 are placed to urge the ridges outwardly. Conveniently, these ridges may be formed by channel metal members 82 within which resilient slabs 83 are placed and clamped. These resilient slabs 83 are made of any heat resistant material such as neoprene or the like. Removable stopping members, not shown, may be provided to limit the outward movement of ridge members 10 and 11 to the positions shown in Figure 5. The channel members 82 have a more snug fit in the grooves 77 and 78 than is diagrammatically shown in the drawings. The ridge members 10 and 11 move toward each other and close the end 9 of the throat as shown in Figure 6 before the full travel of the bars toward each other has taken No air can enter or leave the throat through the end 9 during the remainder of the operation.

Vacuum chamber opposed cavities 13 and 14 are made in the bars 5 and 6 and extend inwardly from the faces 7 and 8. These faces surround the cavity to form opposed rims of the divided vacuum chamber 78. A piercing pin 16 includes a slender or thin body 94 and a relatively large head 95 which is adapted to pierce the sides 1 and 2 of the throat and to form apertures 17 in the sides 1 and 2 through which a slow restricted flow of air may flow outward from the interior of body 4 and throat 3 into the vacuum chamber 78. The slender body 94 insures that some flow of air is possible through the apertures 17, and past the slender body 94, since the head 95 pierces larger apertures than the diameter of the slender body 94.

Regardless of the original form of the throat, the throat becomes a flat, double-sided, tightly squeezed, and closed throat when the stage shown in Figure 6 has been reached.

A source of sub-atmospheric pressure is provided, for example in the form of an automatically controlled vacuum pump construction 15 (Figures 2, l3 and 14) which has an automatic pressure operated switch 15a (Fig. 13) which starts and stops the electric motor 151; of the vacuum pump 15c, and maintains a vacuum of predetermined low pressure in an accumulator tank 15d in said pump construction. The operation of such pump is maintained by plugging in the plug 101 to a source of electrical power. A pump construction of this character is a conventional element now on the market and need not be further described or illustrated. If desired, the accumulator tank 15d and the pressure operated switch 15a may be omitted and the vacuum pump 15c and motor 151) may be operated continuously. A solenoid operated, snap-acting, valve 102, to provide relatively free flow of air, is connected by the large suction conduit 103 with the vacuum pump construction 15. If desired, a vacuum gage 104 is placed in this line to indicate the vacuum being maintained by the pump. A relatively large suction line 105, leading fronrthe valve 102, has branches 106 and 107 which are connected respectively to the longitudinal passagew'ays 168 and 109 in the bars 6 and 5. The solenoid valve 102 is a well known article of commerce and need not be further described. If desired, the passageways 108'and 109 may extend the full length of the bars, and the idle ends may be plugged at 108a and 109a. This permits connection of the pump construction to either end of the apparatus.

The solenoid valve 162 is controlled by a snap-acting switch 110, which is longitudindally adjustably mounted on one of the members 243 and has a lever 111 carrying a roller 112 which trips the switch as it rides over the edge 113 of the bar 5 when the bar 5 has moved toward the bar 6 substantially to the position indicated by Figure 7. Any other type of tripping members may be used between the switch no and the bar 5, if desired. The switch 110, for example, such as is known on the market as a Microswitch, is connected by the cables 114 to energize and open the solenoid valve 102 when the bars 5 and 6 have approached each other substantially to the position shown in Figure 7. The switch 110 is connected by proper wiring (shown in dotted lines in Fig. 2) with the plug 115 which is plugged into any suitable source of power and which also energizes the heaters 115a (Fig. 13) in bar 5 by wires passing into notches 116 and controlled by ad justable thermostats 117 which maintain the bar Sat the desired temperature to produce a sealing action between the throat sides 1 and 2 as hereafter described.

The operator is informed when the bars 5 and 6 have been placed in the position shown in Figure 7 (forex ample, a distance of inch apart) by the snap action impact noise of the solenoid valve tea which is opened by the switch 115 when the bars 5 and 6 are in the position of Fig. 7 and which impact noise can be heard by the operator. However, any other warning signal or automatic control, or the like, may be used to stop the bar 5 at this point. This position is held for a sufiicient length of time to produce the desired vacuum in the bag 4. During this time a low vacuum pressure is produced in the chamber cavities 14 and 13 which preferably are circular in transverse cross section. Sincethe interior of the body 4 and the throat 3 is substantially at atmospheric pres-sure at the first stages of this evacuation, the throat sides 1 and 2 aremoved outwardly by such atmospheric pressure actin'g against the vacuum produced between the faces 7 and 8 and the outer sides 1 and 2 of the throat 3. Such action maintains the interior of the throat open, as indicated in Figure 7 and automatically produces an efficient air flow restricting action between the faces 'iand 8 and the outer sides 1 and 2 of the throat. Air from the interior of the body 4 then flows in a relatively restricted manner through the apertures 17 and past the thin pin body 94 into the cavities 13 and 14. This action continues until the desired vacuum is produced within the body 4. During this time, a substantial portion of the throat 3 is maintained open and tins opening action is enhanced or aided by the fact that the velocity of atmospheric air tending to pass between the faces 7 and 8 and the throat sides 1 and 2 is transformed into kinetic energy, which aids in reducing the head pressure of the air to this point, because of well known physical laws.

While a spacing of inch for the bars 5 and 6 has been indicated as satisfactory during the action taking place in Figure 7 with bags made of aluminum foil of .0035 inch to .0015 inch thickness, it is to be understood that this spacing may be varied somewhat with satisfactory results. The spacing may be compensated for various bag materials, a satisfactory spacing being readily observed by operation of the apparatus.

After the desired vacuum has been obtained in the body 4;" which will be apparent to the operator by the collapse or"- the walls of the body 4 around the contents 61 to the desired degree, the handle 18 is moved further to produce the bar positions shown in Figure 8. The faces 7 and 8 have been pressed to their final position which bring the throat sides 1 and 2 against each other and they are sub- 6 jected to the heat of'the bar 5 (:and/orbar' 6;, irdesired): The interior surfaces of the throat wa'llsl and- 2previ ously have been provided with a heat sealing coating which is rendered active upon being heated to the correct t'emperature by the bar'S and/or 6. For example, the walls l and 2 have been coated with polyethylene which be comes adhesive when heated by the heaters within the barS. Thus, a hermetic seal is provided between the main body 40f the package or bag, and the apertures 17 which have been previously formed in the sides of the throat. If desired, the sealing action may extend to'the end- 9 of the throat. a

The machine may be placed in vertical or horizontal position on the supporting block or the like. That is, the end frame members 20 may be in a vertical or horizontal position. If they are placed in a horizontal position, the face seen by the viewer of Figures 1 and 3 preferably is" placed downwardly, and that seen in Figure 2 is placed upwardly. The bag 4 is placed between the bars 5 and 6,: as shown in dotted'lines inFigure 3 with the throat end 9 adjacent the ridges'iitl and .11. The contents 61 of the bag extend approximately up to the sinuous dotted line 13am Figure 3, or as shown in full lines in Figures 5 and 7. The contents 61 are brought near to the faces 68 and 69 (Figure 5) to insure substantial sealing of the sides" 1' and Z almost to the edge of the contents 61. The contents 61 aid in maintaining the throat walls separated during: the evacuating stage of Figure 7. Various widths of'b'ags. 4 may be placedbetweenthe bars 5 and 6,- since the parallel faces 7 and 8 of the bars form extensions from the vacuum cavity 13, 14 a sufiicient distance to aeco'm modate-bags of many different widths.

Figures 4' and 9 show another embodiment of a face on the stationary bar. The face/8a isformed' on the resilient strip 8b, which, forexia'mple, is made of silicone rubber or other resilient material not harmed by the temperatures attained in this apparatus; The strip Sb'is einbedded'in the wedge-shaped groove of the stationary bar 6a: Otherwise all of the other elements, such as the mov able bar 5, therid'ges 1i) and" 1:1, pin 1'6, etc. niay'be substantially the same in shape and mode of operation-as previously described with respect to Figures-l-S; The resilient strip 8b provides the yielding" and adjustable face 8a which takes up any irregularities in the appa-y ratus or in the bag, to insure a more uniform action during the evacuating and sealing operations.

' Figure 10 is an enlarged transverse cross-section of a the operating mechanism automatically produces a'cycle" of operations to produce relative movement between the I supporting members 5 and 6 from a separated starting po V V sition, such as shown in Figures 5 and 14, automatically to move the members 5 and6 through the-positions shown in Figures 5, 6, '7 and 8 to close the end ,of the. throat of the bag, to produce a zone of relatively low vacuum in the cavities -13 and 14 and between the fiace'sf 7 and-8 and the outer surfaces ofrthe' opposite sides? of-the throat, to reduce the pressure in the throat and. package, to seal the sides of the throat by further'movement of the supporting members 5 and 6 towards each.

other-and to return the opposed members 5 and 6; to the separated starting position shown in Figures *5 and 143* Initiating means are provided to initiate the'cycle of operations, and programrn'eans areprovided automatically to maintain the mechanism-f in operation? throughout the cycle'of operations and then tostop the mechanism automatically at the end of the cycle in readiness to perform another cycle.

To this end, a motor 200 (or any other power source, such as a power driven automatic clutch) is drivingly connected to the opposed movable members and 6 to produce the cycle of operations heretofore described. Initiating means, in the form of a starting switch 202, starts the motor 200.

Program means automatically to maintain the mechanism and motor 200 in operation throughout the cycle and then to stop the motor and mechanism at the end of the cycle in readiness to perform another cycle may be provided. To this end, a holding switch 204, and a vacuum controlling cam 206 are provided. The switch 204 stops the motor 200 after it has completed a cycle which was initiated by a temporary closing of the switch 202 by foot or hand operation at 202a, for example. The vacuum controlling cam 206 operates the snap switch 110 heretofore described to open the snap action solenoid valve 102 heretofore described to produce a vacuum in the cavities 13 and 14 while the members 5 and 6 are substantially in the position shown in Figure 7. The cam 206 again operates the switch 110 to disconnect the vacuum source by the snap acting valve 102 while the member 5 is returning to its starting position.

Specifically, the mechanism or apparatus shown in Figures 14 through 17 includes a base 210 of which the gear casing 212 is mounted, for example, by the foot construction 214 which is bolted or otherwise attached to the base 210. The gear casing 212 supports the motor 200, which drives the worm gears 218 and 220 within the casing 212. The gear 220 drives the shaft 222, which has a hearing at 224 on the casing 212 and a bearing at 226, which may have a bearing support connected to the base 210. The shaft 222 drives the cam 228. The construction is such that when the starting switch 202 is temporarily closed by foot or hand operation, the motor 200 is started and automatically rotates the cam 228 from the starting position 230 of cam 228, counter-clockwise, for example, until the earn 228 makes a complete revolution and returns to the starting point 230, whereupon the motor 200 automatically stops and holds the apparatus in starting position, in readiness to perform another cycle.

The members 5 and 6 have opposed faces 7 and 8 movable substantially as heretofore described through the positions shown in Figure 5, 6, 7 and 8. At the starting position shown in Figure 14, the downwardly directed upper bar flat face 7 and the upwardly directed lower bar fiat face 8 lie in planes which are slightly angular with respect to each other; but when these faces 7 and 8 reach the position shown in Figure 8, they are substantially parallel, since they have reached their closest relative position.

Other elements are shown in Figures 14 through 17 which are identified by reference characters below the number 200, and all of the elements so identified have the same construction and operate substantially in the same manner as correspondingly identified members in the previous Figures 1 through 13 except as obviously modified by the constructions shown in Figures 14 through 17. For example, the upper movable supporting member 5 is movable with respect to the member 6 by the operation of cam 228. To this end, the member 5 is held by the arms 234. These arms 234 are connected to the member 5 by welding or the like at the juncture point 236. The arms 234 are rockingly supported on or pivoted by the shaft 238, which may rock on supports 240, which in turn are conveniently supported on the subbase 242, secured to the main base 210. Alternatively the arms 234 may rock on shaft 238, which may be stationarily held by the supports 240.

Preferably, the arms 234 are secured to each other by the bridging member 244 and support the rotatable pulley 246 by means of'the shaft 248 which is supported by the bearing heads 250 at the ends of the arms 234. The pulley 246 rides on the cam 228 and is raised and lowered thereby, and this action in turn conversely raises and lowers the member 5 by the rocking movement of the arms 234 about the axis 238a of the shaft 238. The arms 234 and the sub-base 242 have spring holding means or cups 252 and 254 respectively to hold the compression springs 256. These springs maintain the pulley 246 against the cam 228 and insure proper movement of the member 5 and arms 234, as is apparent.

During normal operation, the member 6 preferably is substantially stationary throughout the cycle of operations. Preferably, the member 6 is vertically adjustable to compensate for varying thicknesses of the bag material at the throat 3. Also, if desired, the member 6 is resiliently supported in a manner to be substantially unyielding during the normal cycle of operation, but to be yielding if any obstruction is inadvertently placed between the members 5 and 6 during such cycle of operation.-

To this end, the member or bar 6 may be connected to a flat longer bar 260 by means of the screws, welding or the like. The bar 260 is supported by a strong elastic construction such as by the bar 264 made of any resilient material such as neoprene, or the like. Alternatively,

, the bar 260 may be supported by a plurality of compression helical springs 266, shown in Figure 17. The bolts 268 may conveniently be countersunk at 270 with their heads 272 held therein in rotationally fixed manner. The bolts 268 pass through the plate 260, and plate 264 if desired, and have their upper ends threadedly engaged by any well known lock nut construction 274 to provide the slight vertical adjustment required to compensate for varying thickness of bag material and also initially properly to position the member 6 with respect to the member 5.

In the construction shown in Figure 17, the bar 260 may be substantially the same as in Figures 14 through 16. However, the resilient bar 264 is omitted, and in lieu thereof the helical compression springs 266 surround the bolts 268 and support the bar 260 resiliently above the base 210.

The earn 228 has an eccentric construction to produce the positions shown in Figures 5 to 8 for the proper and desired time as the cam is rotated through one complete revolution by the motor 200. To this end, the eccentric cam surface at 230 is at a minimum distance from the axis 276 of the shaft 222. The cam surface 278 from the point 230 to the point 280 gradually increases in distance from the axis 276 gradually to move the member 5 from the position at Figure 5 to the position of Figure 7. The cam surface 282 from the position 280 to the position 284 is a dwell segment, which preferably remains equally distant from the axis 276, as indicated by the dotted equal length radii 281, to maintain a dwell or pause of the required length in the position of Figure 7. The cam surface 286 gradually increases from the point 284 to the point 288, which is the point of maximum eccentricity, and corresponds to the position of Figure 8. If desired, a short equally distant surface at 289 to the point 290 is provided having equally long radii 291 to maintain the members 5 and 6 in the position of Figure 8 sufficiently long to provide and insure thorough heat sealing of the bag throat. The cam surface 292 from the position 290 to the starting point 230 gradually decreases in eccentricity to return the member 5 to the separated starting position shown in Figures 5 and 14.

The axis 238a of the shaft 238 preferably lies in the plane of the surface 7 of member 5. The member 6 is vertically adjusted by movement of the locknuts 274 so the plane of the surface 8 of member 6 is slightly below the axis 238a a distance substantially equal to, or infinitely less than the thickness of the two sides 1 and 2 of the package throat 3 when in the fully compressed condition of Figure 8. This insured proper compression and heat sealing of the sides 1 and 2 to each other.

The initiating means, or starting switch 202 may have a knob or pedal 202a which may be downwardly pressed by hand or foot to close the double contact movable member 293 against the action of the compression spring 294 which has its other end stationarily held by the support 296. The switch 202 is temporarily closed, for a relatively short period of time,or instant, temporarily to connect the electric source or plug 298 with the motor 200 through the lines 300 and 301 a sufficient length of time to close the holding switch 204.

The program means includes a holding switch 204. This may have the movable double contact arm 304 reciprocated by the lever 306 fulcrumed at the stationary point 308. The lever 306 is downwardly biased by the compression spring 310 which has its other end stationarilyheld' by the stationary support 312. The cam 3131 is driven in unison with cam 228 by interlocked shafts 222 and 311. Cam 313 has a starting position lifting knob 314 which opens-the switch 204 when the cam 228- has its starting position 230' in engagement with the pulley 246, as shown in Figure 14. The remaining surface 316 of earn 204 is equally distant from the axis 276, and permits the double contact arm 304 to close upon the stationary contacts to connect the source of power or electric plug 298 with the motor 200 through the lines 318 and 319. This holding switch construction maintains the motor 200 in operation to produce one complete revolution of the earn 223 from the time that the knob 314 moves out of contact with the lever 306' after the temporary closing of switch 202. Thereafter, the switch 204 holds the motor 200 in operation until the cams 228 and 313 make a complete revolution and bring the knob 314 again in contact with the lever 306 to stop the motor 200. The switches 204 and 202 at this time are in open position. Switch 204 is opened by cam 316 and switch 202 had been previously released to the open position by the user after the temporary closing thereof during the starting operation.

The cam construction 206 automatically connects the cavities 13 and 14 of the members and 6 with the vacuum source 15 preferably from the time that the cam 228 comes in contact with the pulley 246 at the point 320, preferably just ahead of the point 280. The cam '6 automatically maintains the vacuum connection until the cam 22S comes in contact with the pulley 246 at the point 322, preferably a short interval of time after it has contacted at the point 290. This is accomplished, for example, by providing the lever 324, which is fulcrumed at 326 and has one end in contact with the cam surfaces 328 and 329. The point 330 on earn 206 corresponds with point 320 on cam 228 and the point 331- on earn 206 corresponds with point 22 on cam 22%.

The lever 324 is downwardly urged by the compression spring 332', which has its other end held by the stationary support 334. The lever 324 is connected by a link or other construction 336 with the switch 110, which is a snap switch and substantially identical in operation with the switch 110 heretofore described in connection with Figures 1 through 13, except that the switch 110 of Figtlre 14 is not operated directly by movement of the memher 5. When cam points 320 and 330 reach operative positions, the switch 110 is energized to open valve 102, and when cam points 322 and 331 reach operative positions, the switch 110 closes the valve 102.

The cams 206 and 311 may be driven in unison with earn 228 by interlocking the cam shafts 222 and 311 in any desired manner. For example, the cams 222 and 311 may be mounted on shaft 311 within a switch box 340 and the shaft 311 may be keyed into shaft 222. The box 340 may also contain the switches 204 and 110'.

In the embodiment of Figure 17, the switch 110 may be made automatically operable directly by movement of the member 5. The switch 110 is supported by the member 6 of Figure 17 and has a contact lever or button 340. A. vertically adjustable actuating member or screw 342 ish'eld by the U-shaped bracket 344, which is secured-ft? the member 5. The screw 342 is threaded in the a'rriis 345 of the bracket 344. A suitable lock-nut holds the screw in adjusted position and permits calibration of the screw 342 to obtain the desired switch operating position. The abutment member 340 is a yielding lever or plunger movable into switch 110, as is obvious.

In the operation of the construction shown in theFigures 14 through 16, the user places the throat 3 of the bag 4, as shown in Figures 5 to 8, between the'member's- 5 and 6 and then temporarily closes the switch 202 by a temporary downward pressure of the foot or hand. This starts rotation of the motor 200 until the knob 314 is moved away from the lever 306, almost instan taneously, to close the holding switch 204. Thereafter, the switch 202 is released by the user. The motor 200 thereafter is energized by holding switch 204, and continues to rotate and drive the cam 228, 313 and 206 throughout one complete revolution. The cam 228' rocks the arms 234 and thereby moves the member 5 downwardly through the position shown in Figures 5 to 8, and then back to the position shown in Figure 5, whereupon the knob 314 once again opens the holding switch 302' and-stops the cycle of operation. The field bag, which is sealed as previously described, is removed and the new bag is inserted between the members 5 and 6, whereuponthe switch 202 again is temporarily closed for starting another cycle of operation.

The foregoing description discloses a method and apparatus for vacuum sealing the sides of the throat of a" package in which the throat 3 is inserted between two: relatively simple bars 5 and 6, and in which the .end 9" of the throat is closed by the ridges 10 and 11. The apertures'17 are formed when convenient. The bars 51 and'6 are brought together by motion of either bar, or

both bars, to a position shown in Figure 7 where the faces 7 and 8 of the bars are close together, but are a suflicient' distance to permit a free passage of air from the main body of the bag 4'through the throat 3, and through the apertures 17 while a relatively low vacuum is being main tainedin the cavities 13 and 14. This causes a flow of air from the inside of the bag 4 through the throat 3,. through apertures 17, past thin body 94 of pin 16, and into the cavities 13 and 14. The low vacuum pressure extends along the outer surfaces of the sides 1' and of the throat '3 and along the faces 7 and 8' of the bars 5 and 6 to maintain a substantial portion of the throat 3 in open condition, as shown in Figure 7. This insures the production of the desired vacuum in the contents 61" of the bag 4. Thereafter, the bars 5 and 6 seal the sides. 1 and 2 by further movement toward eachother, as indicated in Figure 8, where a thermal sealing action takes place, if desired, by the action of the heaters, now

shown, and located in the bar 5 and/ or 6. This is an im-' proved, yet simple and effective construction and method, a

statutes, it is to be understood that other forms and em bodiments of the invention may be used, in accordance with the scope of the claims which follow.

What we claim is:

1. An apparatus for vacuum sealing a double-sided evacuating throat of a package comprising: a pair of supporting members relatively movable with respect to each other and having opposed faces to receive said throat between them, said faces being substantially paral- .lel when moved to their closest relative position; throat end closing ridges. extending from said faces and having resilient mounting means to cause said ridges to meet and close the end of said throat before the full relative travel pressure source and connections from said source to. said cavities; a piercing pin in one of said cavities to pierce restricted apertures in' both sides of said throat during the relative travel of said supporting members; and mechanism to produce relative movement between said supporting members to close the end of said throat, to pierce said restricted apertures in said throat, to produce a zone of relatively low vacuum in said vacuum chamber and between said faces and the outer surfaces of said sides of said throat, to reduce relatively slowly the pressure in said throat and package by outward flow of air through said apertures, and then to seal the sides of said throat to each other.

2. An apparatus for vacuum sealing a double-sided evacuating throat of a package comprising: a pair of supporting members relatively movable with respect to each other and having opposed faces to receive said throat between them, said faces being substantially parallel when moved to their closest relative position; throat end closing ridges extending from said faces and having resilient mounting means to cause said ridges to meet and close the end of said throat before the full relative travel of said members toward each other; walls forming vacuum chamber opposed cavities in said faces; a vacuum pressure source and connections from said source to said cavities; a piercing pin in one of said cavities having a thin supporting body and an enlarged piercing head to pierce restricted apertures in both sides of said throat during the relative travel of said supporting members; and mechanism to produce relative movement between said supporting members to close the end of said throat, to pierce said restricted apertures in said throat, to produce a zone of relatively low vacuum in said vacuum chamber and between said faces and the outer surfaces of said sides of said throat, to reduce relatively slowly the pressure in said throat and package by outward flow of air through said apertures and past said thin supporting body, and then to seal the sides of said throat to each other.

3. An apparatus for vacuum sealing a double-sided evacuating throat of a package comprising: a pair of supporting members relatively movable with respect to each other and having opposed faces to receive said throat between them, said faces being substantially parallel when moved to their closest relative position; throat end closing ridges extending from said faces and having resilient mounting means to cause said ridges to meet and close the end of said throat before the full relative travel of said members toward each other; walls forming vacuum chamber opposed cavities in said faces; a vacuum pressure source and connections from said source to said cavities; a flow control valve in said connections, a piercing pin to pierce restricted apertures in both sides of said throat during the relative travel of said supporting members; and mechanism to produce relative movement between said supporting members to close the end of said throat, to pierce said restricted apertures in said throat, to open said valve to produce a zone of relatively low vacuum in said vacuum chamber and between said faces and the outer surfaces of said sides of said throat, to reduce relatively slowly the pressure in said throat and package by outward flow of air through said apertures, and then to seal the sides of said throat to each other.

4. An apparatus for vacuum sealing a double-sided evacuating throat of a package comprising: a pair of supporting members relatively movable with respect to each other and having opposed faces to receive said throat between them, said faces being substantially parallel when moved to their closest relative position; heating means for one of said supporting members; throat end closing ridges extending from said faces and having resilient mounting means to cause said ridges to meet and close the end of said throat before the full relative travel of said members toward each other; walls forming vacuum chamber opposed cavities in said faces; a vacuum pressure source and connections from said source to said cavities; a piercing pin in one of said cavities to pierce restricted apertures in both sides of said throat during the relative travel of said supporting members; and mechanism to produce relative movement between said supporting members, to pierce said restricted apertures in said throat, to produce a zone of relatively low vacuum in said vacuum chamber and between said facesand the outer surfaces of said sides of said throat, to reduce relatively slowly the pressure in said throat and package by outward flow of air through said apertures, and then to heat seal the sides of said throat to each other.

5. An apparatus for vacuum sealing an evacuating throat of a package comprising: a pair of supporting members relatively movable with respect to each other and having opposed faces to receive said throat between them, said faces being substantially parallel when moved to their closest relative position; yieldable throat end closing means extending from said supporting members to cause said closing means to close the end of said throat before the full relative travel of said supporting members toward each other; walls forming vacuum chamber opposed cavities in said faces; a vacuum pressure source and connections from said source to said cavities; a piercing pin in one of said cavities to pierce a restricted aperture in the side of said throat during the relative travel of said supporting members; and mechanism to produce relative movement between said supporting members to close said throat, to pierce said restricted aperture in said throat, to produce a zone of relatively low vacuum in said vacuum chamber and between said faces and the outer surfaces of opposite sides of said throat, to reduce rela-. tively slowly the pressure in said throat and package by outward flow of air through said aperture, and then to seal the opposite sides of said throat to each other.

6. An apparatus for vacuum sealing a double-sided evacuating throat of a package comprising: a pair of supporting members relatively movable with respect to each other and having opposed faces to receive said throat between them, said faces being substantially parallel when moved to their closest relative position; throat end closing ridges extending from said faces and having resilient mounting means to cause said ridges to meet and close the end of said throat before the full relative travel of said members toward each other; walls forming vacuum chamber opposed cavities in said faces; a vacuum pressure source and connections from said source to said cavities; a

. piercing means to pierce a restricted aperture in one of the sides of said throat;-and mechanism to produce relative movement between said supporting members to produce a zone of relatively low vacuum in said vacuum chamber and between said faces and the outer surfaces of said sides of said throat, to reduce relatively slowly the pres sure in said throat and package, by outward flow of air through said aperture, and then to seal the sides of said throat to each other.

7. An apparatus for vacuum sealing an evacuating throat of a package having a main body comprising: a pair of elongated bars movable relatively to each other and having opposed faces to receive said throat between them, said faces being substantially parallel when moved to their closest relative position; throat end closing means adjacent said faces; walls forming vacuum chamber opposed cavities in said faces; a piercing device to pierce a restricted aperture in said throat; a source of sub-atmospheric pressure; means to connect said cavities to said source; and mechanism to produce a cycle of operations including relative movement between said bars from a separated starting position for controlled distances to pierce a restricted aperture in said throat, to produce a zone of relatively low pressure vacuum in said vacuum chamber and between said faces and opposite sides of the outer wall of said throat, to reduce relatively slowly the pressure in said throat by restricted outward flow of air through said aperture into said vacuum chamber until the desired vacuum is obtained in said throat, then to seal said throat between aperture and the main body of said package and to return said bars to said starting position.

8. The method of vacuum sealing a package having contents in a main body surrounded by air at atmospheric pressure, and having a double-sided evacuating throat connected to the interior of said main body, which comprises: closing the outer end of said throat; providing small restrictive apertures in the side Walls of said throat; loosely surrounding the outer surfaces of said throat with opposed rims of a vacuum chamber; reducing the pressure in said chamber to produce a relatively low pressure zone around the outer surfaces of the side walls of said throat while the insides of the throat and the main body of each package remain at a higher pressure and arereduced in pressure by -a relatively restricted flow of airthrough said apertures into said chamber to maintain the throat inopen condition until the desired vacuum is produced within said package; and then sealing said throat between-said apertures and said main body ofisaid package.

9. The method of vacuum sealing a package having contents in a main body surrounded by air at atmospheric pressure, and having a double-sided evacuating throat connected to the interior of said main body, which comprises: closing the outer end of said throat; providing -a' small restrictive aperture in a side wall of said throat; loosely surrounding the outer surfaces ofboth sides of said throat with opposed rims of a vacuum chamber; reducing the pressure in said chamber to produce a relatively low pressure zone around the outer surfaces of the side walls, of said throat while the insides of the throat and the main body of said package remain at a higher pressure, and are reduced in pressure by a relatively restricted flow of air through said aperture into said chamber thus to maintain the throat in open condition until'the desired vacuum is produced within said package; andthen sealing said throat between said aperture and said'main body of said package.

10. The method of vacuum sealing a package having contents: in a main body surrounded by air at atmospheric pressure, and having a double-sided evacuating throat connected to the interior of said main body, which coniprises: closingthe outer end of said throat; providing small restrictive apertures in the side walls of said throat; loosely surrounding the outer surfaces of said throat with opposed rims ofavacuum chamber; reducing the pressure in said chamber. to produce a relatively low pressure zone around the outer surfaces of the side walls of said throat aidedby high velocity flow of outside air between said rims and outer surfaces and into said chamber while'the insides of the throat and the main body of said package remain at a higher pressure and are reduced in pressure by the relatively restricted flow of air through said ertures into said chamber thus to maintain the throat in open condition until the desired vacuum is produced within said package; and then sealing said throat between said'apertures and said main body of said package.

1.1. The method of vacuum sealing apackage havingcontents in'a main body surrounded by air at atmospheric pressure, and having a double-sided evacuating throat connected to the interior of said mainbody, which comprises: closing the outer end of saidthroat; providing asmall restrictive aperture in; a side wall of said throat; loosely surrounding the outer surfacesof both sides of said throat with opposed rims of a vacuum chamber; reducthe'pressurein: said chamber-to produce a relatively low pressure zone around theouter surfaces of the side walls of said throat" while the insides of the throat and themain body of said package remain at a higher pressureand aretrelatively slowly reduced in pressure by restricted flow of air through said aperture into said chamber thus, to maintain the-throat in open. condition until the desired vacuum is produced within said package; and then sealing said throat between said aperture and said mainbody of said packageby movement of said rims toward each other.

12. An! apparatus for. vacuum sealing the tubular throat of a'package having its contents within a main 1 4 a body of said package connected to said throat 'comprising: a pair of elongated bars, one of said bars being movable relatively to the other, said bars having opposed substantially fiat faces to receive said throat betweenthem, said faces being substantially parallel when moved to their closest relative position; opposed throat end closing ridge members mounted on said bars and extend-- of sub-atmospheric pressure; means to connect said cavities with said source to produce a low pressure zone in said chamber andtbetween said rims and the outer surface of said throat; and mechanism to move said bar" controlled distances and to control the connection of said vacuum chamber to said source of sub-atmospheric pressure to close the end of said throat, to pierce an aperture in said throat, to produce a zone of relatively low pressure vacuum in said vacuum chamber and between said rims and the outer wall of said throat' and to reduce relatively slowly the pressure in said throat and body by restricted: flow of air outward through said aperture into said chamber until the desired vacuum is: obtained in said body, and then to seal said throat be tween said aperture and said main body.

13. An apparatus for vacuum sealing the tubular throat of a package having its contents within a main body of said package connected to said throat compris ing: a pair of elongated bars, one of said bars being movable relatively to the'other, said bars having opposed substantially flat faces to receive said throat" between them, said-faces being substantially parallel when moved to their closest relative position; opposed throat end closing ridge members mounted on said bars and: extending in front of said opposed faces, at least one of said ridge members being resiliently mounted and closing the'end of said throat before the full travel of said one bar; walls forming vacuum. chamber opposed cavities in said faces, said faces surrounding said cavi ties to form opposed rims of said vaccum chamber; aiercing device having an enlarged head and thin bodyin said vacuum chamber to pierce restricted apertures in said throat during movement of said bar and to permit a restricted flow of air through said apertures; a' source of sub-atmospheric pressure; means to connect said cavities with said source to produce relatively quickly a low pressure zone in said chamber and between said rims and the outer surface of said throat; and mechanism to move said bar controlled distances and to control the connection of said vacuum chamber to said source of sub-atmospheric pressure to close the end of said throat, to pierce an aperture in said throat, to produce a zonev of relatively low pressure vacuum insaid vacuum chamber andbetween said rims and the outer wall of said throat and to reduce relatively slowly the pressure in said throat and body by restricted flow of air through said apertures into said chamber until the desired vacuum is obtained in said body, and thento seal said throat between said aperture and said main body. I

14. An apparatus for vacuum sealing the tubular hroat of a package having its contents within a main body of said package connected to said throat compris= ing: 'a pair of elongated bars, one of said bars'being movable relatively to the other, said bars having opposed substantially flat faces to receive said throat be-' tween them, said faces being substantially parallel when moved to their closest relative position; heating 'means for one of said bars; opposed throat end closing ridge. members mounted on said bars and extending in front of said opposedifaces, at least one ofsaid ridge mem bers being resiliently mounted and closing'the end'of' said throat before the full travel of said one bar; walls forming a vacuum chamber opposed cavities in said faces, said faces surrounding said cavities to form opposed rims of said vacuum chamber; a piercing device to pierce a restricted aperture in said throat; a source of sub-atmospheric pressure; means to connect said cavities with said source to produce relatively quickly a low pressure zone in said chamber and between said rims and the outer surface of said throat; and mechanism to move said bar controlled distances to close the end of said throat and to produce a zone of relatively low pressure vacuum in said vacuum chamber and between said rims and the outer wall of said throat and to reduce relatively slowly the pressure in said throat and body by restricted flow of air through said aperture into said chamber until the desired vacuum is obtained in said body, and then to heat seal said throat between said aperture and said main body.

15. An apparatus for vacuum sealing the tubular throat of a package having its contents within a main body of said package connected to said throat comprising: a pair of bars, one of said bars being a movable bar'movable relatively to the other, said bars having opposed substantially flat faces to receive said throat between them, said faces being substantially parallel when moved to their closest relative position; a throat end closing ridge member mounted on one of said bars and extending in front of said opposed faces, said ridge members being resiliently mounted and closing the end of said throat, before the full travel of said movable bar; walls forming vacuum chamber opposed cavities in said faces, said faces surrounding said cavities to form opposed rims of said vacuum chamber; a piercing device in said vacuum cham- -ber to pierce restricted apertures on opposite sides of said throat during movement of said movable bar; a source of sub-atmospheric pressure; means to connect said cavities with said source to produce relatively quickly a low pressure zone in said chamber and between said rims and the outer surface of said throat; and operating means to move said movable bar controlled distances from a separated starting position to control the connection of said vacuum chamber to said source of sub-atmospheric pressure to close the end of said throat, to pierce an aperture in said throat, to produce a zone of relatively low pressure vacuum in said vacuum chamber and between said rims and the outer wall of said throat, and to reduce relatively slowly the pressure in said throat and body by restricted flow of air through said apertures into said chamber until the desired vacuum is obtained in said body to seal said throat between said aperture and said main body.

16. An apparatus for vacuum sealing a throat of a package comprising: a pair of supporting members relatively movable with respect to each other and having opposed faces to receive said throat between them, said faces being substantially parallel when moved to their closest relative position; throat end closing ridges extending from said faces and having resilient mounting means to cause said ridges to meet opposite sides of said throat and to close the end of said throat before the full relative travel of said members toward each other; walls forming vacuum chamber opposed cavities in said faces; a vacuum pressure source and connections from said source to said cavities; piercing means to pierce a restricted aperture in the side of said throat; and mechanism to produce relative movement between said supporting members to close the end of said throat, to produce a zone of relatively low vacuum in said cavities and between said faces and the outer surfaces of said opposite sides of said throat, to reduce the pressure in said throat and package by outward flow of air through said aperture from the interior of said throat to said vacuum chamher, and then to seal said sides of said throat by further relative movement of said supporting members toward.

each other.

17. An apparatus for vacuum sealing a throat of a package comprising: a pair of supporting members relatively movable with respect to each other and having op posed faces to receive said throat between them, said faces being substantially parallel when moved to their closest relative position; a throat end closing ridge ex from said source to said cavities; piercing means to pierce a restricted aperture in the side of said throat; and mechanism to produce relative movement between said supporting members to close the end of said throat, to produce a zone of relatively low vacuum in said cavities and between said faces and the outer surfaces of said opposite sides of said throat, to reduce the pressure in said throat and package by outward flow of air through said aperture from the interior of said throat to said vacuum chamber, and then to seal said sides of said throat by further relative movement of said supporting members toward each other.

18. An apparatus according to claim 15 in which said operating means includes a manually operable lever and cam.

19. An apparatus according to claim 15 in which said operating means includes initiating means to initiate operation of said operating means; and program means to maintain said operating means in operation to complete the sealing of said throat and to return said movable bar to said separated starting position.

20. Apparatus according to claim 7 in which said mechanism includes initiating means to initiate said cycle of operations, and program means automatically to maintain said mechanism in operation throughout said cycle and then to stop said mechanism with said supporting members in said separated starting position in readiness to perform another cycle.

21. An apparatus according to claim 7 in which said mechanism includes an electric motor drivingly connected to produce said cycle of operations, a starting switch to,

start said motor, and holding switch to maintain said.

end of said cycle.

22. An apparatus according to cla1m 7 in which said mechanism includes a base, a shaft supported on said base, a rocker arm construction pivoted by said shaft, one of said bars being supported on said base, the other of said bars being carried by said arm construction, a rotatable cam actuating said rocker arm construction during one complete revolution of said cam to cause relative movement of said bars from said separated starting position to throat sealing position and to return said bars to said starting position, said cam being shaped to pro duce said cycle of operations.

23. An apparatus according to claim 7 in which said mechanism includes a base, a shaft supported on said base, a rocker arm construction pivoted by said shaft, one of said bars being supported on said base, the other of said bars being carried by said arm construction, a rotatable cam actuating said rocker arm construction during one complete revolution of said cam to cause relative movement of said bars from said separated starting position to throat sealing position and to return said bars to said starting position, said cam being shaped to produce said cycle of operations, said mechanism also including initiating means to initiate rotation of said cam, and program means automatically to maintain said rotation of said cam during said complete revolution and then to stop said cam at the end of said revolution.

24. An apparatus according to claim 7 in which said mechanism includes a base, a shaft supported on said base, a rocker arm construction pivoted by said shaft, one of said bars being supported on said base, the other of said bars being carried by said arm construction, a rotatable cam actuating said rocker arm construction during one complete revolution of said cam to cause relative movement of said bars from said separated starting position to throat sealing position and to return said bars to said starting position, said cam being shaped to produce said cycle of operations, said mechanism including an electric motor drlvingly connected to rotate said cam, a starting switch to start said motor, and a holding switch to maintain said motor in operation throughout said complete revolution of said cam after said starting switch has been released and then to stop said motor at the end of said complete revolution.

No references cited. 

